This application claims priority from Korean Patent Application No. 2003-24330, filed on Apr. 17, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to an apparatus and method for enhancing the accuracy of a sensor signal, and more particularly, to an apparatus and method for enhancing the accuracy of a sensor signal by compensating for bias and controlling tolerance of the sensor.
2. Description of the Related Art
Generally, a sensor signal exhibits drift with respect to time. Also, there is an offset, which needs to be compensated for, in a measured value through a sensor due to an inner bias or an outer bias such as noise. In addition to compensating for bias, tolerance may also need to be considered. Since a bias or a tolerance cannot be obtained through the sensor, sensor error may be corrected after finding the cause, or through an error estimating algorithm, to increase the accuracy of values measured by the sensor.
FIG. 1 is a block diagram of a bias compensating apparatus disclosed in U.S. Pat. No. 5,825,350. In the bias compensating apparatus of FIG. 1, a low-pass filter (LPF) 10 extracts a low-frequency signal from a sensor signal, and a differentiator 11 differentiates the low-frequency signal. A window comparator 12 determines whether or not the differentiated signal is included within a window of a predetermined size. A latch 13 stores a signal output from the LPF 10, and outputs the stored signal, in response to a signal output from the window comparator 12. A subtractor 14 subtracts the signal output from the latch 13 from the signal output from LPF 10 to output a final bias. According to a conventional apparatus for controlling a tolerance of a sensor, a sensor signal is determined to be the one when the sensor signal is greater than a predetermined reference value. However, since this bias compensating apparatus uses a single large-sized window comparator, a bias may not be compensated for, even when the sensor is not in operation.
Since a conventional apparatus for controlling tolerance has a fixed dead zone, namely a tolerance range, a predetermined part of a sensor signal is regarded as a noise which causes signal loss. As a result, it is increasingly likely that the sensor will not operate correctly.